alpha-Tocopherol specifically inactivates cellular protein kinase C alpha by changing its phosphorylation state.

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Ricciarelli R, Tasinato A, Clement S, Ozer NK, Boscoboinik D, Azzi A

alpha-Tocopherol specifically inactivates cellular protein kinase C alpha by changing its phosphorylation state.

Biochem J. 1998 Aug 15;334 ( Pt 1):243-9. doi: 10.1042/bj3340243.

PubMed ID

9693126 [ View in PubMed

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Abstract

The mechanism of protein kinase C (PKC) regulation by alpha-tocopherol has been investigated in smooth-muscle cells. Treatment of rat aortic A7r5 smooth-muscle cells with alpha-tocopherol resulted in a time- and dose-dependent inhibition of PKC. The inhibition was not related to a direct interaction of alpha-tocopherol with the enzyme nor with a diminution of its expression. Western analysis demonstrated the presence of PKCalpha, beta, delta, epsilon, zeta and micro isoforms in these cells. Autophosphorylation and kinase activities of the different isoforms have shown that only PKCalpha was inhibited by alpha-tocopherol. The inhibitory effects were not mimicked by beta-tocopherol, an analogue of alpha-tocopherol with similar antioxidant properties. The inhibition of PKCalpha by alpha-tocopherol has been found to be associated with its dephosphorylation. Moreover the finding of an activation of protein phosphatase type 2A in vitro by alpha-tocopherol suggests that this enzyme might be responsible for the observed dephosphorylation and subsequent deactivation of PKCalpha. It is therefore proposed that PKCalpha inhibition by alpha-tocopherol is linked to the activation of a protein phosphatase, which in turn dephosphorylates PKCalpha and inhibits its activity.

DrugBank Data that Cites this Article

Drugs

D-alpha-Tocopherol acetate

Drug Targets

Drug	Target	Kind	Organism	Pharmacological Action	Actions
Vitamin E	Serine/threonine-protein phosphatase 2A catalytic subunit alpha isoform	Protein	Humans	Unknown	Not Available	Details
Vitamin E	Serine/threonine-protein phosphatase 2A catalytic subunit beta isoform	Protein	Humans	Unknown	Not Available	Details